U.S. Pat. No. 7,682,117 B2 discusses an isolating holder for connecting a fuel distributor rail of a fuel injection system for the direct injection of fuel into an internal combustion engine, in order to reduce the transmission of noise and structure-borne noise from the fuel distributor rail to the engine structure, by realizing an elastic decoupling. The advantage is a reduction in the audible noise of the fuel distributor rail. Clamping elements are provided, which face each other, serve as pretension delimiters and have a damping ring made of an elastomer assigned in each case. In the fastening, the axial pretensioning excursion is delimited via a gap between the clamping elements.
In the holder from U.S. Pat. No. 7,682,117 B2, it is therefore possible to use two annular elastomeric components in conjunction with two metal sleeves for the damping, while the pretension is restricted. The restriction is adjustable via the predefined gap. The gap is bridged in the screw fitting, and the annular elastomeric components are pretensioned. As soon as the metal sleeves reach a hard stop, the additional screw pretension is no longer introduced into the elastomeric components but rather into the metal components. This protects the elastomeric components against overexpansion and against failure when the tightening torques are too high.
However, the holder from U.S. Pat. No. 7,682,177 B2 has the disadvantage that due to the tolerances of the individual components of the elastomer components and the metal sleeves, especially with regard to the height dimensions, tolerance-related variances in the prestretching come about in the elastomer components in the assembled state. In particular when the elastomer components are implemented as thin-layer elastomer components, they are very sensitive with regard to this tolerance chain, which causes the dimensional play to be lost. For the maximum boundary samples pretensioned the most for tolerance-related reasons are especially at risk of tearing, whereas the corresponding minimum boundary samples result in a clamping force that is too low with respect to a holder body. On the other hand, the use of elastomer components having random flexibility is also disadvantageous because this results in higher, quasi-statistical displacements of the fuel distributor and the fuel injectors with regard to the introduction of operating forces, which in turn leads to higher wear at the seals, especially at the seals with respect to a fuel injector. In addition, there is the disadvantage that a tangential movement of the elastomer material toward the rigid metal surface occurs at the boundary layers between the elastomer components and the metal sleeves. This results in heavy abrasion of the elastomer at the contact surfaces, and thus to a high risk of failure.